This invention relates to a method for transferring working conditions parameters of computer numerical control (CNC) machines and in particular to one for transferring the working conditions parameters of a computer numerical control EDM (electric discharge machining) device by using the PLC (programmable logic controller) ladder under the control of the CNC system to simulate the output signals generated by hardware so as to transfer the most working conditions parameters with the least output terminals.
For the machine manufacturing industry, conventional machining is significantly dependent upon the experience of workers. With the advent of the CNC machines, high machining precision can be repeatedly achieved not only by experienced workers but also by inexperienced workers with CNC machines, such as a CNC wire EDM and a CNC EDM device. An EDM device uses electric sparks and arcs to erode and thus remove metal from a work piece. The energy of the discharge directly affects the working efficiency, electrode wear and surface roughness of the work piece. Therefore it is necessary to adjust the discharge parameters, such as ON time, OFF time, high voltage current, low voltage current, gap voltage and servo sensitivity, so as to obtain the optimum machining. In an automatic system, the controller has to control not only the feed of the machine tools but also the change and switch of parameters in different machining periods. The conventional EDM device and the NC (.numerical control) EDM device, even some of the CNC EDM devices, although being capable of adjusting the parameters, possess different disadvantages. For example,
(1) For the conventional EDM device, it needs a complicated control panel which is difficult to operate and has to be operated manually and furthermore its sophistication in wiring and arranging elements increases the manufacturing cost;
(2) For the NC EDM device, it needs hardware to set, store and transfer working conditions parameters and because of the hardware, it is hard to modify and expand and is inflexible;
(3) For the general CNC EDM device, its control is done by direct I/O (input/output) and thus needs a great number of output terminals for transferring data which increases the sophistication of wiring.
Since EDM comprises a variety of working conditions parameters and each parameter has several different variations, choosing an efficient way to transfer working conditions parameters is of vital importance for automatization.